Apple modified its lawsuit against Amazon this week, accusing the giant e-tailer of infringing its "App Store" trademark in new advertising for the Kindle Fire tablet.

"Amazon began altering its use of the infringing mark by omitting or de-emphasizing the use of the 'for Android' suffix to the 'Amazon Appstore' phrase," Apple charged in the amended complaint filed Wednesday in a California federal court.

Apple and Amazon have been in a legal battle since mid-March, when Apple sued Amazon for trademark infringement over the latter's use of "appstore."

Apple submitted a trademark application for "App Store" with the U.S. Patent and Trademark Office in 2008. That application is pending, awaiting resolution of opposition from Microsoft.

Apple tied Amazon's change to "Amazon Appstore" to the launch of the Kindle Fire, the 7-in. tablet that went on sale this week.

"When Amazon announced in late September 2011 that it would introduce a new hardware product named the Kindle Fire (the 'Fire'), Amazon promoted the Fire's ability to use Amazon's mobile software download service but omitted the 'for Android' phrase when using the APPSTORE mark," Apple said in the revised complaint.

The complaint included a screenshot of Amazon.com that showed an advertisement for the Kindle Fire that used the phrase "Amazon Appstore -- thousands of popular apps and games."

Amazon has since changed the ad copy, omitting "Amazon Appstore" from that section of the page. Lower on that same page, however, it used the phrase to describe where Fire users could obtain email apps.

Apple also contended that Amazon's shorter name for its mobile application distribution service was also being used to promote gift cards.

"Amazon's ongoing unlawful use of the APP STORE mark has irreparably harmed Apple, and Amazon's threatened expansion and/or alteration of that unlawful use will increase the irreparable harm to Apple," Apple's lawyers claimed in the new complaint.

Apple faces other disputes over its App Store mark.

Amazon currently uses the name 'Amazon Appstore' only once on the sales page for the new Kindle Fire.

Last January, Microsoft asked the U.S. Patent and Trademark Office to deny Apple's application, arguing that because the term is generic, competitors should be able to use it.

Microsoft's attempt to nullify Apple's App Store trademark is currently on hold because of the Apple v. Amazon lawsuit, according to recent documents published by the U.S. Patent and Trademark Office.